The causal relationship between immune cells mediating FIT3L, CCL4, OSM, and skin‐derived deteriorated tumors.

Objective: Observational studies have identified a dual effect of circulating inflammatory proteins and immune cells on cancer progression. However, the specific mechanisms of action have not been clarified in the exacerbation of cutaneous‐origin tumors. Therefore, this study aims to investigate whether the causal relationship between circulating inflammatory factors and basal cell carcinoma (BCC), cutaneous malignant melanoma (SKCM), and cutaneous squamous cell carcinoma (cSCC) is regulated by immune cells. Methods: This study employed the Two‐Sample Mendelian Randomization (TSMR) approach to investigate the causal relationships between 91 circulating inflammatory factors and three prevalent types of skin cancer from a genetic perspective. Bayesian Weighted Mendelian Randomization (BWMR) was also used to validate correlation and reverse MR to assess inverse relationships. Subsequent sensitivity analyses were conducted to limit the impact of heterogeneity and pleiotropy. Finally, the two‐step Mendelian Randomization (two‐step MR) method was utilized to ascertain the mediating effects of specific immune cell traits in the causal pathways linking circulating inflammatory factors with BCC, SKCM, and cSCC. Results: The Inverse Variance Weighted (IVW) method and the Bayesian Weighted Algorithm collectively identified nine inflammatory factors causally associated with BCC, SKCM, and cSCC. The results from Cochran's Q test, mendelian randomization pleiotropy residual sum and outlier (MR‐PRESSO), and MR‐Egger intercept were not statistically significant (p < 0.05). Additionally, the proportions mediated by CD4+ CD8dim T cell %leukocyte, CD4‐CD8‐Natural Killer T %T cell, and CD20 on IgD‐CD38‐B cell for FIt3L, CCL4, and OSM were 9.26%, 8.96%, and 10.16%, respectively. Conclusion: Immune cell levels potentially play a role in the modulation process between circulating inflammatory proteins and cutaneous‐origin exacerbated tumors. This finding offers a new perspective for the in‐depth exploration of cutaneous malignancies. [ABSTRACT FROM AUTHOR]